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  1. #include <stdio.h>
  2. #include <unistd.h>
  3. #include <sys/types.h>
  4. #include <string.h>
  5.  
  6. #define BUFFER_SIZE 25
  7. #define READ  0
  8. #define WRITE 1
  9.  
  10. int main(void)
  11. {
  12.   pid_t pid;
  13.   //open two pipes, one for each direction
  14.   int mypipefd[2];
  15.   int mypipefd2[2];
  16.  
  17.   /* create the pipe */
  18.   if (pipe(mypipefd) == -1 || pipe(mypipefd2) == -1) {
  19.     fprintf(stderr,"Pipe failed");
  20.     return 1;
  21.   }
  22.  
  23.   /* now fork a child process */
  24.   pid = fork();
  25.  
  26.   if (pid < 0) {
  27.     fprintf(stderr, "Fork failed");
  28.     return 1;
  29.   }
  30.  
  31.   if (pid > 0) {  /* parent process */  
  32.     int writeValue=10;
  33.     int readValue=0;
  34.     close(mypipefd[READ]);      //close read end, write and then close write end
  35.     write(mypipefd[WRITE],&writeValue,sizeof(writeValue));    //write to pipe one
  36.     printf("Parent: writes value : %d\n", writeValue);
  37.     close(mypipefd[WRITE]);
  38.     close(mypipefd2[WRITE]);        //close write end, read, and then close read end
  39.     read(mypipefd2[READ],&readValue,sizeof(readValue));
  40.     printf("Parent: reads value : %d\n", readValue);
  41.     close(mypipefd2[READ]);
  42.   }
  43.   else { /* child process */
  44.     int writeValue=20;
  45.     int readValue=0;
  46.     close(mypipefd[WRITE]);   //close write end, read, and then close read end
  47.     read(mypipefd[READ],&readValue,sizeof(readValue));
  48.     printf("child: read value : %d\n", readValue);
  49.     writeValue+=readValue;
  50.     close(mypipefd[READ]);
  51.     close(mypipefd2[READ]);       //close read end, write and then close write end
  52.     write(mypipefd2[WRITE],&writeValue,sizeof(writeValue));
  53.     printf("child: writeValue value : %d\n", writeValue);
  54.     close(mypipefd2[WRITE]);
  55.  
  56.   }
  57.  
  58.   return 0;
  59. }
  60.  
Success #stdin #stdout 0s 10320KB
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stdin
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Standard input is empty
stdout
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child: read value : 10
child: writeValue value : 30
Parent: writes value : 10
Parent: reads value : 30
https://ideone.com/Eb8YTZ
language:
C (gcc 8.3)
created:
7 years ago
visibility:
public

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